SCIENCE-GOSSIP. 



139 



left. The peristomial band of cilia is large and 

 strong. The cilia of the general body surface are 

 very fine and short, and arranged in longitudinal 

 rows. An oval macronucleus and many micro- 

 nuclei are present. The main contractile vacuole 

 is situated near the anterior end, and into it run 

 two collecting canals ; of these one lies round the 

 front border under the peristome, the other is 



carried directly backwards towards the posterior 

 end. The anus is situated immediately in front of the 

 contractile vacuole. The whole body is beset with 

 numerous blackish pigment granules. The animal 

 when e.xtended is about 300 microns in length. 



This species lives in bog water, and encysts in a 

 thick pear-shaped cyst. 



(To be continued.) 



CHAPTERS FOR YOUNG NATURALISTS. 



[Continued from page 13.) 



THE INFINITELY LITTLE. 

 By J. O. Symes, M.D. 



npHE rush and hurry of modern everyday life, 

 the exacting demands of social duties and 

 athletic pursuits, leave to most of us but little 

 time for the study of nature, unless, indeed, it be 

 human nature. The habits and instincts of wild 

 animals are to most men a sealed book, and 

 their knowledge of the life-history and develop- 

 ment of the smaller insects is such as has been 

 gleaned from the pages of a popular magazine. 

 Such, then, being the case, it is not wonderful 

 that with regard to still more minute forms of 

 life the most profound ignorance is almost 

 universal. I refer more particularly to those 

 microscopic organisms classified under such terms 

 as microbes, bacilli, bacteria, etc. It was not 

 until the introduction of the microscope that the 

 existence of such creatures was even suspected. 

 The discoverer of that instrument soon observed 

 and described some of those lower forms of life 

 which we now call germs, the first specimens to be 

 distinguished being obtained from scrapings of his 

 teeth. It was not, however, until the early part of 

 the nineteenth century that the microscope became 

 fully developed, and to what a pitch of excellence 

 it has reached we may judge from the fact that 

 lenses are now made capable of magnifying the 

 size of an object 3,000 to 5,000 times. If it were 

 possible to view a man under such a power he 

 would appear about the height of Mount Everest, 

 and a child would cap the highest Alpine peak. 



The modern microscope has opened up a new 

 world to us, and made plain phenomena which 

 to our fathers were matters for the wildest conjec- 

 ture or the most insoluble mystery. As further 

 progress is made with the mechanical and optical 

 details of the instrument it is possible, and indeed 

 probable, that still more minute forms of life, in 

 comparison with which diatoms will be as moun- 

 tains and germs as elephants, will come to our 

 knowledge, and will necessitate the revision of all 

 our present ideas. 



For a long period it was thought that germs 

 and ferments, which are the terms generally 



applied to these minute organisms, arose spon- 

 taneously ; that they were the creation of dirt or of 

 dead matter of any kind. In proof of this assertion 

 it was pointed out that materials which had been 

 boiled for a time, and in which all organisms were 

 presumably dead, would, even if kept in sealed 

 vessels, undergo eventually putrefaction or fer- 

 mentation, and that they then could be shown 

 to be crowded with germs, which could only 

 have arisen from the materials themselves. It 

 is as if we were to expect seeds to be manufac- 

 tured from garden mould, or eggs from the gravel 

 of the hen-house. It took years to dissipate this 

 belief ; but eventually the work of Tyndall, of 

 Huxley and of Pasteur established the fact that 

 there is no such thing as spontaneous generation. 

 Each germ is and must be the offspring of a pre- 

 existing germ, inheriting from it its physical 

 peculiarities, its habits and its tastes. These 

 workers showed that if a flask containing, say, a 

 solution of sugar, were boiled for a short period for 

 a succession of days, so as to destroy not only any 

 germs that might be present, but also their spores 

 or eggs, then, if properly corked with cotton wool 

 so as to prevent the entry of any but filtered air, 

 the contents would keep indefinitely. Directly, 

 however, such contents were exposed to germ- 

 laden air, then and then only would fermentation 

 begin. Microbes are not, then, manufactured 

 from lifeless material ; they do not arise spon- 

 taneously, but are] the products of pre-existing 

 organisms. 



It is not, however, remarkable that the theory 

 of spontaneous generation should have been so 

 strongly supported, for germs are practically 

 ubiquitous. " We breathe bacteria, drink bacteria, 

 eat bacteria, and our bodies are the happy hunting- 

 grounds of countless myriads of them." Earth, 

 air and water swarm with them, and they are even 

 to be found in the frozen hail and falling snow. 

 Dust is the great carrier of microbes — the two are 

 inseparable. The number found in any given 

 sample of air will thus vary according to the place 



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